Zero-Dimensional Stacking Domains Enable Strong-Ductile Synergy in Additive Manufactured Titanium

TL;DR

This paper uncovers how zero-dimensional stacking domains in oxygen-modified titanium, identified through advanced electron ptychography, significantly enhance strength and ductility by promoting slip diversity and work hardening, offering new alloy design strategies.

Contribution

It introduces zero-dimensional stacking domains as a new defect type in additive manufactured titanium and links them to improved mechanical properties through atomic-scale imaging.

Findings

ZDSDs are prevalent in oxygen-modified titanium.

ZDSDs enable three-fold increase in strength and ductility.

Interstital solutes can be used to enhance alloy properties.

Abstract

Alloying by addition of oxygen interstitials during additive manufacturing provides new routes to strengthen and toughen metals and alloys. The underlying mechanisms by which such interstitial atoms lead to enhanced properties remain, however, unclear, not least due a lack of quantitative atomic-scale models linking microstructure to properties. Here using quasi-3D imaging based on multi-slice electron ptychography, we reveal the importance of a new type of interstitial-character lattice defect, namely zero-dimensional stacking domains (ZDSDs), present in high density in AM-processed oxygen-modulated pure titanium. These ZDSDs promote slip diversity, and support intense work hardening, enabling a three-fold enhancement in both strength and ductility in Ti-0.45O compared to conventional pure Ti. The work demonstrates the potential for using interstitial solutes to enhance mechanical properties in a range of critical engineering alloys.